This invention is directed to a control system for detecting the presence of packages that may accumulate on a rollerless conveyor that provides long accumulation zones in the conveyor without sacrificing accumulation density so as to simplify accumulation control zones for sensing packages that may be moved along the conveyor.
The prior art of accumulating packages on a conveyor wherein the package is moved along a plurality of rollers by a chain that is elevated to support the package for movement relative to frame members has means to support the package in a stationary position when not lifted by the chain for transportation to an outlet. Such a conveyor is disclosed in Wyman U.S. Pat. No. 3,930,573 of Jan. 6, 1976.
A variation in the prior art is disclosed in Bowman U.S. Pat. No. 3,934,707 of Jan. 27, 1976 which employs a continuously drawn belt with ways alongside the belt which are movable vertically to vary the relative vertical position between an accumulation position wherein the support surface of the ways is above the conveyor belt causing package accumulation and a package drive position wherein the support surface of the way is below the conveyor belt causing package movement.
The prior art includes a conveyor system of the character in Holt U.S. Pat. No. 4,149,626 of Apr. 17, 1979 in which spaced conveyor surfaces of multiple rollers are occupied by a flat link chain which is vertically movable relative to the spaced roller surfaces at selective portions to move packages.
Furthermore, the prior art Garro U.S. Pat. No. 5,085,311 of Feb. 4, 1992 has disclosed a belt or chain with wear surfaces along both sides of the belt or chain for conveying packages, and apparatus for displacing the belt or chain or the wear surface relative to each other to provide an in-line accumulator having a zero backline pressure.